Experimental and clinical evaluation of a digital flat-panel X-ray system based on cesium iodide (CsI) and amorphous silicon (a-Si).Performance of a prototype detector was compared with conventional screen-film radiography (SFR) using several phantom studies. Foreign bodies, fractures, osteolyses, and pulmonary lesions were analyzed. Additionally, 120 patients were studied prospectively, resulting in 400 comparative X-ray studies. The flat-panel detector was exposed with standard dose and with a dose reduction of up to 75%. Detector size was 15 x 15 cm, pixel matrix was 1 x 1 k with a pixel size of 143 microns. Modulation-transfer function was determined to be 18% at the maximum spatial resolution of 3.5 lp/mm.The diagnostic results achieved with the digital detector were similar to those of conventional SFR, even at reduced radiation exposure. A potential for dose reduction was observed: 50% with respect to osteoarthrosis and fractures, and 75% for determining bony alignment.This new technology can be used in thoracic and skeletal radiography. A significant dose reduction is possible, depending on the suspected disease.